The visual system has been relatively neglected in recent MS research and often it is not even examined in autoposied patients. We propose to study demyelination of the optic nerve clinically and experimentally. We will determine the leukocyte anitgens HL-A in ON and MS patients since the histocompatibility immune system may be linked to the genetic control of susceptibility to disease. We hope to develop a test diagnostic for demylelination through studies of lymphocyte transformation in vitro to CNS antigens. The index of tranformation will be measured quantitatively by an assay of the total uptake of tritiated thymidine. Histopathological studies will be performed on autopsied ON or MS cases when available, but in order to facilitate the morphological and biochemical studies of plaques involving the visual pathways, an experimental in vivo model of demyelination of the optic nerve will be produced in animals.